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PSYC62H3 (280)
Chapter 7

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University of Toronto Scarborough
Suzanne Erb

Chapter 7 Psychomotor stimulants -at low and moderate doses, these druge poduce motor stimulation, reduc fatigue, increase resistance to sleep, increase vigilance and alertness, heightened mood -dose-response functionas typically are inverted U-shaped ; range of doses in which enhancement occurs, but as dose increases, performance returns to nondrug levels or worse -generally, signs of increased sympathetic nervous system (increased heart rate, blood pressure) -none of the terms mentioned adequately describes the effects of these drugs if the drugs are used in large amounts acutely or moderate amounts chronically Minor stimulants-methylxanthines; caffeine and nicotine Motor effects -produce rate-dependent effects on responses; effect of the drug depends on baseline rate of responses generated by the specific category (schedule) -enhance lever pressing when responding on schedules that generate low response rate (fixed interval) -decrease lever-ressing when animals are responding on fixed ratio schedules --low doses=stimulants increase locomotor activity and exploration -as dose gets higher=sterotypy; focused repetitive behaviours, head bobbing, nose poking etc. -major stim-dose increases, increase response frequency increase with decreasing response category Lower doses-locomotion and exploration -forebrain DA systems critical ; double dissociation (for motor stim effects of amph); two distinct brain areas mediate two different behaviours and the effects of selective lesions can dissociate these effects) -kill DA in Nac-supressed locomotor stimulant effects of low doses of amph but did not supress stereptypy seen in high doses -kill DA in caudate/puatamen-reduced stereotypy; enhanced apomorphine stereotypy; resulting in post-syn supersensitivity Rotation model-give stimulants, causes asymmetrical locomotion; direction of rotation is opposite, depending whether stimulant drug acts prsyn (amph) or is an agonist that binds to post-syn (apomorphine) -efect of DA depletions on one side of the brain is to make that side more sensitive less sensitive to effects of amph and to make that same side more sensitive to the effects of a DA agonist (receptor sensitivity) Caffeine -methylxanthines -hard to determine the over time course and impact of caffeine on an individual -act as nonselective antagonist of adenosine receptors; adenosine-acts as an NM affects neuronal excitability (inhibits presyn realease of variety of NT) -caffeine block these receptors-enhances release of NT; increasing circulation of catecholamines -stimulates locomotor activity, can reverse affects of DA antagonist -many of the reinformcing effects of caffeine stem from its ability to terminate caffeine withdrawal biphasic -at low doses- has mood-elevating and fatigue-relieving; larger doses-do not have more elevating mood; display dose-dependent improvements (can be particularly in caffeine deprived); enhance performnace -high doses-may cause insomnia, restlessness and mild sensory disturbances; produces no benefits or decrease performance -typically raises blood pressure Alcohol & caffeine-deleterious effects of alcohol intoxication are not reduced by caffeine; feel more alert but will still be impaired in terms of motor coordination and decision making Nicotine & caffeine-caffeine enhance reinforcing, smokers drink more=increase jitterness; can be a conditioned stimulus triggering tobacco craving -to treat nicotine addiction, must take out caffeine Tolerance -up-regulations of adenosine receptors in the brain Withdrawal-uncommon; except if you take a lot/heavy drinker -headaches most common; rebound effect from caffeine’ -increased fatigue, iriitability Dependence liability-low Nicotine -active ingredient is nicotine; acts as a nicotinic Ach agonist; vehicle for self- administration of nicotine -depression not an antecedent to heavy cigarette use among teens -the psychosocial rewards are strong to maintain smoking behaviour until the individuals learn to monitor the amount of smoke and the unpleasant side effects -nicotine not the only reinforcing factor behind smoking tobacco -ability to reduce negative affective states-transient aversive emotional states occur as a result of enviro etc and nicotine withdrawal -nicotine administered increases synaptic concentrations of dop in Nac=primary reward -more to do with the development of motivational or incentive states than the drug enjoyment -discrete stimuli (smoke upon exhalation) always accompany the nicotine just before it reaches the brain -has a mild psychostimulant effect, enhanced vigilance -Smokers report cigs calming them down, relieves their craving for a cigarette or stops withdrawal -can enhance task performance, memory, cognition and learning in some individuals -nicotine can affect modd, cognition, or arousal; cognition could be enhanced directly by nicotine, or it could be enhanced because nicotine improves the persons mood -finger-tapping rate and motor responding in tests of focused attention enhanced -stimulates nicotinic Ach receptors -in the PNS, nAch found in adrenal gland trigger the release of adrenaline from adrenal gland; transported to adrenergic receptors in the heart and blood vessels; increases in heart rate and elevated blood pressure In CNS, enhances both inhib and excitatory transmission by acting on nAch located on presyn nerve endings; increase concentration of Ca=> enhance release of transmitter -unidentified ingredient in tobacco smoke reduces levels of monoamine oxidase (MAO) in smokers=higher DA levels; enhancing reward pathway ; -long term use of tobacco=nicotine is reinforcing b/c immediately stops withdrawal symptoms (PHYSICAL DEPENDENCE) on nicotine Withdrawal symptoms-decreased heart rate, irritability, increased hunger, sleep disturbances, GI disturbances, drowsiness, headache, impairment of concentration, judgement -long-term nicotine exposure=upregulations of nAch and then quickly desensitized after an agonist binds to it -low levels of nicotine causes significant nAch, receptors enter long-lasting inactive state Withdrawal-slow recovery to functional states from various levels of desentization and inactivation Tolerance-nach undergoing desensitization and inactivation -these symptoms may be more psychological than pharmacological -smokers in a treatment getting placebo reported fewer withdrawal symptoms and smoke fewer cigarettes (IF IT WAS PURELY PHYSIOLOGICAL) -nicotine has both positive (enhancement of mood) and negative (relief of abstinence symptoms) reinforcing properties -smoking tobacco; chewing, not harmless but less harmless than smoking -cant ‘mature out’ of drug habits; quitting requires determination; chewing gum/patches -nicotine patch-easier more effective treatment; easier to use and comply with than gum and induces fewer side effects -use zyban Amphetamines -DOM produce effects similar to those of mescaline but possess considerably higher pote
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